1. Field of the Invention
The invention concerns a firing arrangement for a number of electric valves, particularly thyristors. More specifically, the invention concerns a firing arrangement for electric valves each of whose control path is associated with a firing circuit having a detector capable of detecting electromagnetic radiation and, thus, of being acted upon by wireless means via such radiation generated by a transmitter which is controlled by a firing control signal.
2. Description of the Prior Art
It is already known (German Pat. No. 1,538,099) that an electric valve and, in particular, a thyristor, can be fired using a firing circuit which derives its firing energy from the voltage at the anode-cathode path of the valve itself. In such a circuit, a pulse capacitor is charged by means of this voltage and, when required, is discharged onto the control path of the valve via a switching element. The latter element, in turn, is typically a light-controlled thyristor which is triggered by light radiation from a light source placed some distance away. In this type of firing circuit, the electric potential differences which exist between the light source, as the transmitter of electromagnetic radiation, and the electric valve have no effect on the firing. As a result, such a firing circuit can be used advantageously for firing electric valves being employed with high voltages and, in particular, for firing high-voltage thyristors which are used in static converter arrangements.
In German Patent Application No. P. 23 60 662.4, there is disclosed another technique for the wireless transmission, via electromagnetic radiation, of a firing control signal to a firing circuit which is equipped with a detector for detecting such radiation. With this technique, high-frequency radiation is employed as the electromagnetic radiation. As a result, as with the previous technique, the transmission path is free of most interference, thereby making it also particularly suitable for the firing of thyristors which are being used in the aforementioned static converters.
Typically, for wireless firing of electric valves, a line-of-sight path must exist between the transmitter, on the one hand, and the individual detectors, on the other hand. This is true for optical as well as for high-frequency transmission paths. This line-of-sight requirement places severe limitations on the type of design which can be used for the firing arrangement in which the electric valves are being employed.
It is, therefore, an object of the present invention to provide, in a firing arrangement of the above-described type, more degrees of freedom regarding its design and its mechanical layout without disturbing the ability of the arrangement to transmit firing signals. In other words, an arrangement having more latitude in the physical arrangement of its detectors and firing circuits is to be provided. In this connection, it should be noted that the present arrangement does not require that a line-of-sight path exist between the transmitter and the individual detectors. The last-mentioned factor is important particularly for the transmission of firing signals via a high-frequency transmission path.